1. Field of the Invention
The invention relates to a method of producing alloyed metal contact layers on crystal-orientated semiconductor surfaces by energy pulse irradiation.
2. Prior Art
German Pat. No. 2,825,212 describes a process wherein extremely thin metal layers are applied to a semiconductor substrate by vapor-deposition, sputtering, electrolytic precipitation or ion implantation and such thin metal layers are then irradiated with intense short laser-like pulses so as to become alloyed with the semiconductor surface. In this process, the irradiation parameters must be selected in such a manner that no noticeable diffusion of metal into the substrate occurs. The pulse duration of the laser-like pulses, accordingly, must be in the nanosecond range. This known process is limited to manufacture of extremely thin metal structures as are utilized, for example, in VLSI technology.
In semiconductor technology, one generally selects the surfaces, for example, from silicon materials from which components are to be manufactured, in a plane of a specific privileged crystal orientation.
For example, future thyristors generated with the aid of integrated field effect transistors will contain controllable short-circuits. Accordingly, it is necessary to combine power semiconductor and MOS technology with one another. Typically, &lt;111&gt;-orientated silicon is employed in power semiconductor technology because of its good ability to alloy, while &lt;100&gt;-orientated silicon is utilized as the starting material in MOS technology because other crystal properties are considered more significant in this instance.
A further significant difference is that &lt;100&gt;silicon base material can be more easily drawn and homogeneously doped relative to &lt;111&gt;silicon. Thus, &lt;100&gt;silicon can be manufactured substantially more economically. The utilization of &lt;100&gt;-silicon would, therefore, also be more advantageous for the manufacture of power semiconductor components.
However, the use of &lt;100&gt;-orientated silicon for the manufacture of thyristors encounters difficulties in the alloying between metal layers and silicon. For example, an aluminum-silicon alloying in &lt;100&gt;-orientated silicon surfaces occurs very unevenly so that the negative inhibiting capacity is very different.